FTP Plateau (Another one)

I started riding May '23. I've always kept physically active in some form, strength training, some rowing etc, walked my dog 5 hours a week etc.

I'm 81kg / 181cm and have always had a muscular lean build. I'll be 37 next week.

The first proper test I did was December '23 where 323w for 20 min gave me a 307w FTP. By April '24 this had risen to 315w. I've seen no increase in FTP since then, though I don't bother to test anymore because I feel I can calibrate it well off my training.

Any power PBs i've set in the last 12 months have been modest improvements on the numbers I could do last spring. The one area where I feel i've made the biggest improvements would be TTE at 90-100% of FTP. I've done 290w for 2.5 hours, and 305w for an hour in the last few months.

I typically manage to fit in 7-8 hours a week, I'll almost always get 2x intensity sessions done. I've mixed up the stimulus with intervals to target all of the zones above zone 2. I am disciplined on my zone 2 rides and have no issues staying below power and AeT Zone 2 upper limits.

Have I really hit the limits already this early on in my cycling journey of the FTP I can realistically expect to have with the volume I can do?

Has anyone else experienced a similarly lengthy plateau and then started to see some gains again down the line?